The present invention relates to a finishing mortar for sound-absorbing coating of inner walls, ceilings and the like in buildings either directly on concrete or some other carrying material, but it may also be applied on underlying absorption material for sound such as mineral wool, polyester material, fibre board material and glass granulate.
Different buildings are constructed in different ways. They are large or small and made of such materials as stone, concrete, brick, wood, etc. resulting in different strength, heat insulation and sound absorption in walls, floors and ceilings. In buildings where the heat insulation ability and the sound absorption ability are unsatisfactory walls and ceilings may be covered with further material to improve these unsatisfactory properties. The ceiling is often lowered and the walls are built out, for example with cross bars and covered with a sound-insulating material. The material often consists of wood fibre board discs, minarite discs and gypsum and the insulation may consist of different porous materials such as mineral wool.
The work of improving buildings in this regard is often very expensive and even if the materials for the renovation may be good as such, they are often unsatisfactory in some regard, especially with regard to the sound absorption ability.
It has long been a problem during the building of new constructions and renovation of buildings to be able to line the walls and ceilings in such a way that the sound absorption will be satisfactory while at the same time an aesthetically attractive surface is obtained. This has often, especially in concert houses, conference halls, meeting halls, offices and the like, resulted in a non-uniform covering of the walls since the acoustics from certain walls must be different than from other walls and the like.
Through the international patent application WO 95/30804 a sound absorption system for inner walls, ceilings, etc. in buildings is known which is brought about by applying a first layer of mineral wool on a wall, a ceiling or the like, whereupon a second layer of cotton fibres is applied by spraying, coating or in some other way. The cotton fibres are applied from a water suspension which may also contain other materials such as textile fibres, cellulose fibres from coniferous trees, mica, biolite, etc.
Further suspensions for applying the second layer as above are known, namely such suspensions which are based on a finely ground mica mineral which is bound in an organic colorant or cellulose fibres from coniferous trees mixed with mineral fibres and colorants.
In DE 2 620 865 there is disclosed a composition of construction boards and a method of manufacuring such boards. A main compound in said composition is Portland cement and the production method involves drying and curing in an autoclave and, thus, such composition would not be useful for a mortar composition for in-situ use.
These above-mentioned materials, which may be good as such, can however be improved, especially with regard to sound absorption ability and crack formation and the products have therefore been developed further resulting in the present invention.
Through the present invention the problems with the above materials have been solved and these have been improved by bringing about a finishing cement free mortar for sound-absorbing coating of inner walls and ceilings in buildings either directly on concrete or some other carrying material or on underlying insulation material such as mineral wool, which mortar is characterized in that it mostly comprises cotton fibres and expanded perlite, in the weight ratio between perlite and cotton of 10%-250%, preferably 80%.
According to the invention it is suitable that the perlite is present in fractions having a particle size of 0-1 mm, 0-3 mm or 0-5 mm.
According to the invention the expanded perlite should, before it is mixed in the finishing mortar, have a volume weight of 35-125 kg/m3 depending on the particle size.
According to the invention the finishing mortar may also contain other additives such as textile fibres, plant fibres from coniferous trees, mica, biotite, muscovite or silicates or mixtures thereof in small amounts.
According to the invention it is suitable that the mortar is present as a water dispersion with a content of solids which makes it suitable for spraying or spreading, the content of solids then preferably being 200-300 g/l.